Active Asteroids

Where did Earth’s water come from? 

Active asteroids are small rocky objects in our Solar System that have asteroid-like orbits but comet-like appearances. Active asteroids can have visible tails and comae — the halo of debris that often surrounds comets. These visible features have led scientist to determine that these asteroids have water. They may even be the source of water on Earth. 

Join the Active Asteroids project and search for these unusual asteroids to help map the distribution of water in the solar system and inform future space mining!

Go to Project Website


18 and up







What you’ll do

  • Search images captured by the 4-meter Blanco telescope in Chile to find active asteroid candidates.
  • Connect with professional scientists and other citizen scientists in the project Talk forums.


  • Time to get started: Minutes
  • Equipment: Internet connected mobile device or computer
  • Knowledge: None. In-project training provided.

Get started!

  1. Visit our project website.
  2. Click the “Get started” button and complete the short Tutorial to learn how to identify active asteroids in the images. 
  3. Use your new skills to look for evidence of active asteroids in telescope images.
  4. Communicate with other volunteers!

Learn More

If you’d like to learn more about our project and active asteroids, check out our project website at

Left: A dark blob at the center of the image is surrounded by a paler shadow that is roughly spherical on the left of the blob and spreads out on the right, as if the blob was moving through something from right to left.    and Right image: a tight dark spot in the middle of the frame has a tail of grey material extending down to the bottom left. The tail is darkest near the dark spot, getting increasingly faint with distance.
Left: A coma is the fuzzy glow that forms around orbiting bodies (like comets or active asteroids) when they approach the Sun. This fuzzy glow indicates the vaporization of gases or water resulting from solar heating.

Right: The tails of active asteroids or comets consist of vapor and dust, and can vary in shape, length, and intensity. They may even have multiple tails extending in different directions!
A cartoon asteroid is staring straight out of the frame, with beads of sweat springing off its forehead and a weight in each arm. With eyes wide and mouth open it looks surprised to see you.
A big, slightly oblong, dark and light grey asteroid is moving from the upper right to the lower left, shedding smaller chunks of material and a cloud of dust.
Fewer than 30 active asteroids have been discovered since 1949. Maybe you will help discover the next one!
A tight dark spot in the middle of the frame has two tails of grey material extending down to the bottom left. The longer tail extends toward what would be roughly seven o'clock on a clock face and continues out of the frame. The shorter tail points at roughly eight o'clock on a clock face and only reaches halfway to the edge of the frame. Neon green crosshairs focus attention on the central black spot, which we can assume is the active asteroid itself.
The green cross-hairs mark an active asteroid, clearly identifiable by the two tails that trail it. This active asteroid was found by project participants, who are discussing it in talk:

Get to know the people of Active Asteroids!

Portrait photo of a man wearing glasses.

Jay Keuny

Portrait photo of a smiling man

Chad Trujillo

Photo of man holding a laptop

Colin Orion Chandler